Currently, as a display device, so-called HD (High Definition) with a pixel number of 1920×1080 has been mainstream. On the other hand, there has been also growing demand for a higher-definition display device, and a television device for displaying a 4K2K video and an ultrahigh-definition video having a pixel number which is sixteen times of the HD (7680×4320 pixels) has been also increasingly developed. Note that, 4K2K refers to 4K (4096×2160 pixels) which is defined by a standard specification of digital cinema and QFHD (Quad Full High Definition) having a pixel number which is four times of the HD (3840×2160 pixels).
Moreover, when being connecting to external source device with an HDMI (High-Definition Multimedia Interface) (registered trademark) cable, the display device is able to input a video signal from the source device for displaying. However, the current HDMI specification is premised on displaying a video with resolution which is basically not more than the HD. More specifically, it is impossible in the HDMI version 1.4 which is the latest HDMI specification to transmit and reproduce an ultrahigh-definition video with one HDMI cable. Moreover, the HDMI version 1.4 is compatible with a format of 3840×2160 pixels and 30 Hz/25 Hz/24 Hz or a format of 4096×2160 pixels and 24 Hz, but not with 60 Hz, as to a 4K2K video. Accordingly, when a 4K2K video is set, for example, in a personal computer (PC) or the like to try to reproduce a video with 60 Hz in a window by using one HDMI cable, frame omission occurs and smoothness is lacking.
In this manner, it is basically impossible to read a 4K2K or ultrahigh-definition video from source device using one HDMI cable for reproducing, and connection with a plurality of HDMI cables becomes necessary for such reproduction. For example, a display device that displays a 4K2K video requires four HDMI cables and a display device that displays an ultrahigh-definition video requires sixteen HDMI cables, so that a higher-definition display device requires the extremely increased number of HDMI cables for connection. In addition, a display device capable of multi-screen display by a plurality of video signals from a plurality of source device also requires the extremely increased number of HDMI cables for connection.
Here, if HDMI cables are not connected correctly, a video that a part or all of videos to be displayed in split display areas are exchanged, that is, a video that a part or all of a display screen is deviated is to be displayed, so that it is necessary to be very careful such as by performing connection while perusing an instruction manual. Of course, if a specification for a higher-speed cable is established, such a problem is solved, but connection with an HDMI cable is a key for the meantime.
Patent Document 1 discloses a display system that connects a plurality of displays so as to show like a single high-resolution display. In this display system, the plurality of displays are connected to a display sharing box, a dedicated board is plugged in a PC main body, and the display sharing box is connected thereto. Then, the dedicated board shows the plurality of displays to an OS (Operating System) of the PC main body as if being a single display as well as notifies the display sharing box of information from the OS, and the display sharing box judges on which display the information of the OS is to be displayed and provides each display with data.